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The upgraded iMacs Apple announced yesterday include the enhancements that could have been reasonably predicted: faster PowerPC G4 processors running up to 1.25 GHz, faster 333 MHz DDR memory, faster NVIDIA graphics. However, a welcome surprise was the adoption of the faster USB 2.0 standard.

The new iMacs offer two FireWire 400 and three USB 2.0 ports.

There has been controversy over whether Apple should support USB 2.0, which some suggest could undermine third-party developer support for Apple’s own FireWire high speed I/O interface. That isn’t a baseless concern, but I have contended all along that boycotting USB 2.0 would be counterproductive in the bigger picture.

While USB 2.0 does compete to some degree with FireWire, the new FireWire 800 has leapfrogged substantially ahead of USB in raw throughput performance, and the preponderance of USB 2.0 peripherals being made available in the PC sector should be an option for Mac-users. It’s just too large a world to be ignored.

If there is some particular USB 2 peripheral device you would like to use with your Mac -- perhaps to share between a Mac and a PC, then it is convenient to have USB 2 support on your Mac. (Note that most USB 2 devices will work with the USB 1.1 ports in current Macs, but a lot more slowly than they would with real USB 2 support). Make sure that any necessary device drivers are available for the Mac OS before investing in USB 2 hardware.

USB 2 peripherals include: hard drives, HD enclosures, hubs, networking devices, and digital video devices, and are expected to eventually include a vast range of devices such as CD burners, printers, scanners, digital cameras, PDAs, speakers, and Web cams.

Universal Serial Bus 1.x has been the external connectivity standard for both Macs and PCs, having displaced both Serial and ADB standards on the Mac with the introduction of the original iMac in 1998. Indeed on the early iMacs and iBooks, USB displaced SCSI as well, sort of, since those machines had no FireWire ports, but USB 1 is a poor substitute for either SCSI or FireWire, since it is quite slow for data transfers.

USB 2 is engineered to be the answer to USB 1’s leisurely performance, and is also referred to as Hi-Speed USB. USB 2.0 can transfer data between the computer and peripherals up to 40 times faster than original USB, offering nominal transfer rates up to 480Mbps (megabits per second) compared to USB 1.1 devices, which transfer at a poky 12Mbps. While it would take 1.1 minutes to download a 100 MB file with a USB 1.1 device, with USB 2.0 the same transfer would only take 1.6 seconds.

Its development backed by Compaq, Hewlett Packard, Intel, Lucent, Microsoft, NEC and Philips, USB 2 was only originally intended to go as fast as 240Mbps but the speed was raised to 480Mbps. (Apple’s FireWire 400 technology offers transfer speeds of 400 Mbps). The USB 2.0 specification inherits USB 1’s plug and play and hot-swapping capability as well as providing backward compatibility for USB 1.1 hardware. Users can still connect up to 127 devices to a single computer by adding hubs to create more USB 2.0 ports.

USB 2 support is built into Mac OS X, but while some USB 2 adapters will work with OS 8.6 through 9.x, you only get USB 1.1 speeds with the Classic operating systems.

Let’s hope that the entilre Mac computer family gets USB 2.0 support as the upgrade parade proceeds.

Older desktop Macs and PowerBooks with PCI or PC CardBus slots can be upgraded to USB 2.0 support with the appropriate adapter cards which are available from a number of manufacturers.

Charles W. Moore

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